Method and apparatus for casting rotors



Navy L 1949 :1. R. MOLLENHAUER METHOD AND APPARATUS FOR CASTING ROTORSFiled April 12, 1946 3 Sheets-Sheet 1 New 1949 c. R. MGLLENFMUEEZZMETHOD AND APPARATUS FOR ASTING EOTOHS Filed April 12, 1946 3Sheecs-fiheet maims mmrasam- 1949 R. MQLLENHAUER METHOD AND APPARATUSFOR CASTING ROTCJRS Filed April 12, 1946 I Klara-2m JVYUZZEYFZEZEZJ @1 22.2,

Patenteli Nev. 1,1949

ia'ri on AND APPARATUS FOR CASTING no'rons Clarence R. Mollcnhauer,Milwaukee, Wis assigner to The Louis Allis Company, Milwaukee;

Wis., a corporation of Wisconsin Application April 12, 1946, Serial Nb.661,661

6 Claims.

' This invention relates to the manufacture of squirrel cage rotors forelectric motors and refers particularly to rotors having cast conductorbars as shown in Patent Nos. 2,368,295, 2,368,296 and 2,370,458 allissued to S. J. Goran.

As in these patents, the present invention has as its purpose to providean inexpensive and efficient manner of forming radial ventilatingpassages in the rotor during the casting of its conductor bars. Theseradial ventilating passages connect with longitudinally extendingventilating ducts or passages and thus provide for more eifectivedissipation of the heat from the interior of the rotor.

As in the aforesaid patents, the present invention provides for theformation of radial ventilating passages opening to the periphery of therotor betweengroups of laminations and the circumferentially cast rotorbars by which the laminations are held assembled, the groups oflaminations being held in proper spaced relation by lug-likeenlargements formed integrally on the I vention resides in the novelmethod, combination conductor bars between the groups of laminations.

In the methods employed in the aforesaid patents, the production ofthese lug-like enlargements on the conductor bars involves the use ofdestroyable spacing members assembled between the groups of laminations.In one case, these destroyable spacing members are formed of cardboardor similar material capable of being charred or burned away suilicientlyby the hot molten metal to provide mold spaces which form the desiredenlargements, and in the other instance the destroyable members are madeof a material which will withstand the heat of the molten metal butwhich can be subsequently melted or dissolved.

While these past methods have been generally satisfactory, they involveadditional handling of the cast rotor and thus increase the cost ofmanufacture. In contrast, the present invention achieves the desiredresult without entailing such additional handling of the cast rotor andin an exceedingly simple and inexpensive way.

Thus, stated more fully, itis an object of this invention to provide animproved method of casting squirrel cage rotors with radial ventilatingpassages produced during the casting operation and arrangement of partssubstantially as hereinafter described and more particularly defined bythe appended claims, it being understood that such changes in theprecise embodiment of the hereindisclosed invention may be made as comewithin the scope of the claims.

The accompanying drawing illustrate two complete examples of thephysical embodiment of the invention constructed according to the bestmodes so far devised for the practical application of the principlesthereof, and in which:

Figure 1 is a view partially in side elevation and partly inlongitudinal section through a rotor embodying this invention;

Figure 2 is a plan view of a special lamination employed in theformation of the radial ventilatmg passages;

Figure 3. is a detail cross sectional view taken through Figure 2 on theplane of line 3-3;

Figure 4 is a cross sectional view taken through Figure 1 substantiallyon the plane of the. line 4- l, showing a segment of the entire unit;

Figure 5 is a side elevational view of the ass sembled rotor laminationspreparatory to being inserted into the casting mold;

Figure 6 is a longitudinal sectional view through a casting mold withtherotor laminations in position therein preparatory to having theconductor bars cast into the slots;

Figure 7 is a perspective view showing a portion of the cast rotor andillustrating the manner in which the mold forming devices employed inthe casting operation are removed;

Figure 8 is a fragmentary perspective view illustrating one of thelug-like spacing projections which are formed integrally with the rotorbars during the casting of the rotor; and

Figure 9 is a perspective view showing a portion of the speciallamination and the mold forming devices used to produce the lug-likeprojections but illustrating a slightly modified form of mold formingdevice.

Referring now more particularly to the accompanying drawings in whichlike numerals indicate like parts throughout the several views, thenumeral 5 designates the rotor laminations which are punched from thinsheet steel or other suitable material and which are held assembledbetween end rings 6 by a plurality of circumferentially arrangedconductor bars I cast integrally with the end rings. The laminations arepunched to provide a bore 8 for the reception of an armature shaft 9 andto also provide longitudinal air passages or ducts I0. These passages orducs communicate with radial ventilating passages between groups oflaminations held spaced apart at the center by spacing collars l2 and atthe outer periphery of the rotor luglike enlargements |3 formedintegrally with the conductor bars.

The manner in which these lug-like enlargements are produced during thecasting operation constitutes the chief feature of this invention. Tothis end special laminations M are provided. These special laminations(two in the rotor illustrated) are made of the same sheet material fromwhich the regular laminations 5 are punched and have openings l5 andconductor bar slots 6 identical with those of the regular laminations.

However, in addition, each of these special laminations has a ring oftongues projecting perpendicularly from one face or side thereof. Thesetongues H are spaced Slightly radially inward of the inner ends or basesof the conductor bar slots |6 and are radially in line therewith so thata tongue I"! is located adjacent to the inner end of each conductor barslot. While the tongues I? may be separately mounted on the laminationsM in any suitable manner, it is obviously better to form them asintegral parts of the laminations M by striking up the stock provided byopenings I8 out along three (3) sides.

The upstanding tongues or projections I! on the special laminationscoact with mold forming members or forms I9 to define substantiallybox-like molds 20 embracing the conductor bar slots so that the moltenmetal of which the bars are formed will flow from the slots into themolds.

The mold forming members I9 are bifurcated and have substantiallyresilient arms 2| spaced apart a distance greater than the width of theconductor bar slots, and in that embodiment of the invention illustratedin Figures 1 to 8 inclusive the free ends or extremities of the arms 2|have notches or transverse grooves formed in their inner faces toreceive the side edges of the tongues l1. Thus as shown in Figure 2, themold forming members H] can be easily assembled with the laminations |4merely by engaging the notches or grooves 22 with the sides of thetongues and sliding the mold forming members down onto the laminations.

Attention is directed to the fact that the arms of the members I9 are ofsuch length that their connected ends terminate substantially in linewith the peripheral edges of the laminations so that the finishedlug-like enlargement |3 (see Figure 8) will be flush with the outersurface of the rotor.

Attention is also directed to the fact that the height of the moldforming members I9 is equal to that of the tongues After the requirednumber of special laminations (two in the rotor illustrated) have hadthe mold forming members applied thereto in the manner described, thesepreassembled spacing mandrel 24.

units are assembled with the regular laminations on a mandrel 24. Aslightly spiral keyway 25 in the mandrel receives inwardly directed lugsor teats on the laminations so that the conductor slots |6 will beskewed around as required.

In the assembly of the laminations, the groups of regular laminationsare spaced apart at the center by the collars l2 and at the outerperiphery of the assembly by the mold forming members Ill. The completeassembly is then placed in a casting mold as shown in Figure 6.

This mold is of conventional construction and includes a cylinder orwell 26 in which a plunger 21 is reciprocally received. The plunger 21provides the base for the assembled core laminations and is formed toreceive the lower end of the It is to be observed that the base formedby the plunger 21 closes the longitudinal passages I0 at the bottom.Hence molten metal cannot enter these passages.

With the assembled laminations in position as described, sheaths 28 arewrapped around the cylindrical surface of the three (3) groups oflaminations to close the conductor bar slots l6; and then a cap 29 ispositioned on the assembly, which like the plunger 21, is formed toaccommodate the mandrel.

Tie bolts 30 with quick acting latches 3| draw the cap and base orplunger together to place the laminations in compression and hold thesame in intimate contact. The cap 29 and the base or plunger 21 haveannular grooves or channels 32 of a size and shape to form the castrings 6, and the base or plunger has ports 33 leading to its channel 32through which the molten metal enters r the same and rises up into theconductor bar slots during the casting operation.

It is, of course, understood that the assembly of the core structure inthe mold takes place before molten metal is poured into the well orcylinder 2B and that after the assembly is completed the cap which isattached to the plunger 34' of a hydraulic press is raised to lift theentire assembly out of the well to permit ladling the molten metal intothe well. Thereafter the plunger 34 is caused to descend forcing themolten metal up into the conductor bar slots and channel 32 of the cap.Air vents 35 in the cap preclude the entrapment of air and permit metalto rise up into the slots.

As the molten metal rises up into the conductor bar slots, it flows intoand fills the molds 20 to form the lug-like enlargements l3.

After the casting is complete and the metal has hardened, the mold isopened and the assembly is stripped off the mandrel. The mold formingmembers l9 are then forcefully pulled from the assembly as shown inFigure 7. This is readily accomplished as the arms 2| are sufficientlyresilient to allow their outer ends to spread slightly, and also themetal of which the tongues I! are formed is light and soft enough topermit the side edges of the tongues to bend and thus facilitatedisengagement thereof from the notches or grooves 22, since the bentside edges will then cooperate with edges of the notches in the arms towedge the arms apart.

When all of the mold forming members l9 have been so stripped from theassembly, the rotor is complete except for necessary machining. Theradial ventilating passages defined by the spaces between the groups oflaminations and the lug like enlargements on the conductor bars will beof the same size and shape and the sides of the lug-like enlargementswill be neat and smooth surfaced.

In the embodiment of the invention illustrated in Figure 9, theprocedure followed is identical with that described, the only differencebeing that the arms 2| of the mold forming members do not have notchesto engage the side edges of the tongues l1. Instead, the space betweenthe arms 2| is just sufiicient to snuggly engage the sides of thetongues l1 and the members I9 are held assembled with each speciallamination by a ring 7 36 engaged in notches 31 extending across theclosed ends of the bifurcated mold forming members.

From the foregoing description taken in connection with the accompanyingdrawings, it will be readily apparent to those skilled in the art thatthis invention provides an exceedingly simple and inexpensive method ofproducing neatly formed smooth surfaced radial ventilating passages insquirrel cage rotors of the cast type.

What I claim as my invention is:

l. The hereindescribed method of making squirrel cage rotors havingradial air vents between axially spaced groups of laminations and havingcast conductor bars in aligned slots, said conductor bars bridging thespaces between groups of laminations and coacting with the adjacentlaminations to define such vents, which comprises: forming a pluralityof substantially identical laminations, each having a plurality ofspaced apart radial conductor bar slots about its circumference; forminga spacing lamina having conductor bar slots adapted to align axiallywith the conductor bar slots in said first named laminations; formingintegral lugs on said spacing lamina in radial alignment with andinwardly of said conductor bar slots; detachably mounting mold formingmembers on the spacing lamina in juxtaposition to the lugs to definemold cavities closed at their radially innermost ends by the lugs on thespacing lamina and into which the conductor bar slots of the spacinglamina open; stacking numbers of the laminations together in coaxialrelationship and with their conductor bar slots in alignment to form twogroups of laminations; inserting the spacing lamina, with the moldforming members thereon, in place between said two groups of laminationswith the slots of the spacing lamina in alignment with the slots of saidgroups of laminations; holding said groups of laminations spaced apartby means of said mold forming members; casting the conductor bars andsimultaneously filling the mold cavities to form lug-like enlargementson the conductor bars between the groups of laminations; and after thecasting operation is completed, detaching the mold forming members fromthe spacing lamina by'forcefully pulling the mold forming membersoutwardly substantially radially, leaving the spacing lamina in therotor.

2. In the art of making squirrel cage rotors having cast conductor barsembedded in aligned slots of stacked laminations, means for spacinggroups of laminations in the casting of the conductor bars in a mannersuch that lug-like projections will be formed on the bars between thegroups of laminations to hold the same spaced apart, comprising: apunched disc having conductor bar slots like those of the regularlaminations and having a series of circumferentially spaced upstandingtongues on one side of said disc with one tongue opposite the inner endof each conductor bar slot; and a plurality of separate mold formingdevices cooperable with said disc and the tongues thereon to form molds,each of said devices having a pair of arms spaced apart more than thewidth of the conductor bar slots, said arms having grooves in the innerfaces of theiflfree end portions to receive the side edges of theupstanding tongues whereby said devices may be assembled with the discand retained thereon during its assembly with the regular laminations,the side edge portions of said tongues being bendable and the arms ofthe mold forming devices being resilient so that said devices may bepulled oi! the tongues radially after the casting operation.

3. In the art of making squirrel cage rotors having cast conductor barsembedded in aligned slots of stacked laminations, means for spacinggroups of laminations in the casting of the conductor bars in a mannersuch that lug-like projections will be formed on the bars between thegroups of laminations to hold the same spaced apart, comprising: apunched sheet metal disc having a plurality of circumferentially spacedconductor bar slots extending around the periphery thereof and having aring of circumferentially spaced tabs projecting from one side of thedisc, said tabs being formed by striking up the metal of the disc andbeing located adjacent to the inner ends of the conductor bar slots; aplurality of separate mold forming devices cooperable with said tabs todefine lug forming molds, said devices each having a pair of armsadapted to be bridged by one of the tabs; and means for holding saiddevices assembled with the disc with a tab bridging the arms of each ofsaid devices.

4. The hereindescribed method of making a laminated squirrel cage rotorhaving radial air passages between axially spaced portions of the rotorand having conductor bars in axially aligned slots in the rotorlaminations with enlarged portions thereof bridging the space betweensaid axially spaced portions of the rotor to define such passagesandhold said axially spaced portions of the rotor apart, whichcomprises: forming a plurality of substantially identical laminations,each having circumferentially spaced conductor bar slots in itsperipheral portion; forming a spacing lamina having conductor bar slotsadapted to align with the conductor bar slots in said laminations;forming lugs integrally on said spacing lamina in radial alignment withan inwardly of the conductor bar slots in the spacing lamina; detachablymounting mold forming members on the spacing lamina in juxtaposition tothe lugs to define mold cavities closed at their radially inner ends bythe lugs on the spacing lamina and into which the conductor bar slots ofthe spacing lamina open; stacking the laminations and the spacinglamina, with the mold forming members thereon, in coaxial relationship;adjusting the laminations circumferentially to align the conductor slotstherein with one another and with the mold cavities so that the moldcavities open to the conductor bar slots of the adjacent laminations aswell as with the conductor bar slots of the spacing lamina; axiallyclamping the assembled laminations, spacing lamina and mold definingmembers together; injecting molten metal into the conductor bar slotsand the mold cavities to cast the conductor bars with enlarged portionsthereon as defined by the mold cavities and between said axially spacedportions of the rotor; removing the axial clamping pressure; and pullingthe mold forming members radially from between the axially spacedportions of the rotor and the enlargements on the conductor bars.

5. In the art of making squirrel cage rotors having cast conductor barsembedded in aligned slots in stacked laminations, spacing means adaptedto be placed between laminations to hold the same spaced apart whilecasting the conductor bars and for forming lug-like projections on thebars to hold said laminations spaced apart, comprising: a punched sheetmetal disc having a plurality of circumferentially spaced conductor barslots opening to the periphery thereof and having a ring ofcircumferentialiy spaced tabs projecting from one side of the disc, saidtabs being located adjacent to the inner ends of the conductor bar slotsand being formed by striking up portions of the metal of the disc; aplurality of bifurcated mold forming devices cooperable with said tabsto define lug forming molds, each of said devices having its pair ofarms so spaced that the free nds thereof may be bridged by one of thetabs; ,and means engageable with the outer closed ends 1 of all of thedevices for releasably holding the same in cooperative engagement withthe tabs.

6. In the art of making squirrel cage rotors having cast conductor barsembedded in aligned slots of stacked laminations, means for spacinggroups of laminations in the casting of the conductor bars in a mannersuch that lug-like enlargements will be formed on the bars between thegroups of laminations to hold the same spaced apart, comprising: apunched sheet metal disc having a plurality of eircumferentially spacedconductor bar slots extending around the periphery thereof and having aring of circumferentially spaced tabs projecting from one side of thedisc, said tabs being formed by striking up portions of the metal of thedisc and being located in juxtaposition to the conductor bar slots; aplurality of mold forming devices cooperable with saidtabs to define lugforming molds, said de vices each having a pair of arms adapted to formthe side walls of the lug forming molds, said arms being spaced apartmore than the width of the conductor bar slots so that the resulting lugf orming molds are wider than the conductor bar slots, and the tabsbeing wide enough to bridge the space between the inner ends of the armsand thus form the radially innermost walls of the molds;

CLARENCE R. MOLLENHAUER.

REFERENCES CITED The following references are of record in the file ofth' 1 is patent UNITED STATES PATENTS Number Name Date 595,081 ShortDec. 7, 1897 891,906 Card June 30, 1908 917,064 Hibbard Apr. 6, 19091,517,620 Ellis Dec. 2, 1924 1,880,786 Carey Oct. 4, 1932 1,913,138Apple June 6, 1933 1,970,760 McIntire Aug. 21, 1934 1,975,889 WhiteleyOct. 9, 1934 2,176,871 Harrell et al Oct. 24, 1939 2,192,787 Elsey Mar.5, 1940 2,348,511 Armel May 9, 1944 2,368,295 Goran Jan. 30, 19452,368,296 Goran Jan. 30, 1945 2,370,458 Goran Feb. 27, 1945 FOREIGNPATENTS Number Country Date 519,673 France June 14, 1921 5 Co. (1942),page 48.

